Re: porting linux to DSP
Rick Hohensee (humbubba@smarty.smart.net)
Tue, 27 Jul 1999 02:23:23 -0400 (EDT)
>
> Rick Hohensee wrote:
>
> > Another thing I haven't seen mentioned in why Linux on a DSP is absurd is
> > memory management. True multi-user requires hardware-supported
> > sequestering of process memory access. That's why you need a 386+ or
> > 68010+ for any real unix. This is how OSes, mostly unix, have effected the
> > design of the predominant general-purpose CPU chips.
> >
> > Another tiny little issue is that gcc is designed for single-stack
> > register machines. I don't recall gcc.info even bothering to say "oh yeah,
> > Von Neumann architecture." DSPs are Harvard architecture, aren't they?
> > As with stack machines, I'm guessing extending the gcc machine description
> > for Harvard architecture is basically a complete re-write. A quick glance
> > at man gcc doesn't show any DSP-specific options. What gcc can reasonably
> > do is what RTL can reasonably do, Register Transfer Language, used to
> > describe CPU targets. DSPs and Forth engines are not describable in
> > current RTL.
>
> Versions of GCC exist for most major DSP architectures (apart from the low
> end ones). The code isn't exactly production useful, but for a number of
> prototyping activities doing a first pass of at least the non-critical parts
> of the DSP code in C has RAD value.
Oh. Perhaps the original poster would like to know where. My gcc is
2.7.2.3. Is this stuff in later ones?
Why not the low end ones, BTW? That seems contradictory, or are the higher
end ones more like regular CPUs?
>
> What's all the garbage about RTL? Of course an RTL description of any DSP is
> possible. An RTL description of any clocked digital system is possible. How
> the hell do you think the silicon guys design the darned things?
>
gcc (RTL) is geared for single-stack machines. I'm not familiar with the
general case of RTL. I would be surprised even in the general case if a
"Register Transfer Language" was real useful for a stack machine. If you
have some tips on how to describe a 2 or 3 stack machine in gcc RTL I'd be
real interested, without the l-k cc:
This leads to the further problem that C makes lousy Forth and vice-versa,
but I won't mention that :o)
> Steve
>
>
Rick Hohensee
"Fortunately, I keep ma tailfeathers NUMBERED for just such emergencies."
Foghorn Leghorn
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